That's bad enough, but I think his message is louder and more disturbing than that.
Given these two past statements from him,
1: "I will stand with Islam should the political winds change directions" from The Audacity of Hope, and
2. "The future must not belong to those who slander the prophet of Islam." from a speech at the UN,
I believe that by his intentional absence, his message to our European allies clearly was, I will NOT stand with you against radical Islam, and by doing so he tacitly sanctioned the Paris shootings.